Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 133,218	$ 103,992
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,916	45,417
Deferred income tax benefit	(3,035)	(20,651)
Provision for bad debts	278	927
Stock-based compensation expense	16,574	13,903
Excess tax benefits from stock options	(7,030)	(7,801)
Other	149	141
Changes in operating assets and liabilities:
Accounts receivable	12,072	11,965
Other receivables and current assets	19,154	(30,008)
Other long-term assets	(1,580)	(59,757)
Accounts payable, accrued expenses and current liabilities	17	7,608
Accrued income taxes	6,476	80,865
Deferred revenue	14,153	8,716
Other long-term liabilities	(7,315)	36,832
Net cash provided by operating activities	230,047	192,149
Cash flows from investing activities:
Apache acquisition, net of cash acquired	(269,753)	0
Capital expenditures	(12,524)	(9,155)
Purchases of short-term investments	(282)	(1,044)
Maturities of short-term investments	227	7,990
Net cash used in investing activities	(282,332)	(2,209)
Cash flows from financing activities:
Principal payments on long-term debt	(21,260)	(60,315)
Principal payments on capital leases	(70)	(229)
Purchase of treasury stock	(12,704)	0
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,168	1,592
Proceeds from exercise of stock options	14,828	13,060
Excess tax benefits from stock options	7,030	7,801
Net cash used in financing activities	(10,008)	(38,091)
Effect of exchange rate fluctuations on cash and cash equivalents	(3,888)	6,989
Net (decrease) increase in cash and cash equivalents	(66,181)	158,838
Cash and cash equivalents, beginning of period	472,479	335,878
Cash and cash equivalents, end of period	406,298	494,716
Supplemental disclosures of cash flow information:
Income taxes paid	50,505	45,964
Interest paid	$ 1,457	$ 2,538

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Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).